// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/inspector/string-16.h"

#include <algorithm>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <limits>
#include <string>

#include "src/base/platform/platform.h"
#include "src/base/v8-fallthrough.h"
#include "src/conversions.h"

namespace v8_inspector {

namespace {

    bool isASCII(UChar c) { return !(c & ~0x7F); }

    bool isSpaceOrNewLine(UChar c)
    {
        return isASCII(c) && c <= ' ' && (c == ' ' || (c <= 0xD && c >= 0x9));
    }

    int64_t charactersToInteger(const UChar* characters, size_t length,
        bool* ok = nullptr)
    {
        std::vector<char> buffer;
        buffer.reserve(length + 1);
        for (size_t i = 0; i < length; ++i) {
            if (!isASCII(characters[i])) {
                if (ok)
                    *ok = false;
                return 0;
            }
            buffer.push_back(static_cast<char>(characters[i]));
        }
        buffer.push_back('\0');

        char* endptr;
        int64_t result = static_cast<int64_t>(std::strtoll(buffer.data(), &endptr, 10));
        if (ok)
            *ok = !(*endptr);
        return result;
    }

    const UChar replacementCharacter = 0xFFFD;
    using UChar32 = uint32_t;

    inline int inlineUTF8SequenceLengthNonASCII(char b0)
    {
        if ((b0 & 0xC0) != 0xC0)
            return 0;
        if ((b0 & 0xE0) == 0xC0)
            return 2;
        if ((b0 & 0xF0) == 0xE0)
            return 3;
        if ((b0 & 0xF8) == 0xF0)
            return 4;
        return 0;
    }

    inline int inlineUTF8SequenceLength(char b0)
    {
        return isASCII(b0) ? 1 : inlineUTF8SequenceLengthNonASCII(b0);
    }

    // Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
    // into the first byte, depending on how many bytes follow.  There are
    // as many entries in this table as there are UTF-8 sequence types.
    // (I.e., one byte sequence, two byte... etc.). Remember that sequences
    // for *legal* UTF-8 will be 4 or fewer bytes total.
    static const unsigned char firstByteMark[7] = { 0x00, 0x00, 0xC0, 0xE0,
        0xF0, 0xF8, 0xFC };

    typedef enum {
        conversionOK, // conversion successful
        sourceExhausted, // partial character in source, but hit end
        targetExhausted, // insuff. room in target for conversion
        sourceIllegal // source sequence is illegal/malformed
    } ConversionResult;

    ConversionResult convertUTF16ToUTF8(const UChar** sourceStart,
        const UChar* sourceEnd, char** targetStart,
        char* targetEnd, bool strict)
    {
        ConversionResult result = conversionOK;
        const UChar* source = *sourceStart;
        char* target = *targetStart;
        while (source < sourceEnd) {
            UChar32 ch;
            uint32_t bytesToWrite = 0;
            const UChar32 byteMask = 0xBF;
            const UChar32 byteMark = 0x80;
            const UChar* oldSource = source; // In case we have to back up because of target overflow.
            ch = static_cast<uint16_t>(*source++);
            // If we have a surrogate pair, convert to UChar32 first.
            if (ch >= 0xD800 && ch <= 0xDBFF) {
                // If the 16 bits following the high surrogate are in the source buffer...
                if (source < sourceEnd) {
                    UChar32 ch2 = static_cast<uint16_t>(*source);
                    // If it's a low surrogate, convert to UChar32.
                    if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {
                        ch = ((ch - 0xD800) << 10) + (ch2 - 0xDC00) + 0x0010000;
                        ++source;
                    } else if (strict) { // it's an unpaired high surrogate
                        --source; // return to the illegal value itself
                        result = sourceIllegal;
                        break;
                    }
                } else { // We don't have the 16 bits following the high surrogate.
                    --source; // return to the high surrogate
                    result = sourceExhausted;
                    break;
                }
            } else if (strict) {
                // UTF-16 surrogate values are illegal in UTF-32
                if (ch >= 0xDC00 && ch <= 0xDFFF) {
                    --source; // return to the illegal value itself
                    result = sourceIllegal;
                    break;
                }
            }
            // Figure out how many bytes the result will require
            if (ch < static_cast<UChar32>(0x80)) {
                bytesToWrite = 1;
            } else if (ch < static_cast<UChar32>(0x800)) {
                bytesToWrite = 2;
            } else if (ch < static_cast<UChar32>(0x10000)) {
                bytesToWrite = 3;
            } else if (ch < static_cast<UChar32>(0x110000)) {
                bytesToWrite = 4;
            } else {
                bytesToWrite = 3;
                ch = replacementCharacter;
            }

            target += bytesToWrite;
            if (target > targetEnd) {
                source = oldSource; // Back up source pointer!
                target -= bytesToWrite;
                result = targetExhausted;
                break;
            }
            switch (bytesToWrite) {
            case 4:
                *--target = static_cast<char>((ch | byteMark) & byteMask);
                ch >>= 6;
                V8_FALLTHROUGH;
            case 3:
                *--target = static_cast<char>((ch | byteMark) & byteMask);
                ch >>= 6;
                V8_FALLTHROUGH;
            case 2:
                *--target = static_cast<char>((ch | byteMark) & byteMask);
                ch >>= 6;
                V8_FALLTHROUGH;
            case 1:
                *--target = static_cast<char>(ch | firstByteMark[bytesToWrite]);
            }
            target += bytesToWrite;
        }
        *sourceStart = source;
        *targetStart = target;
        return result;
    }

/**
 * Is this code point a BMP code point (U+0000..U+ffff)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.8
 */
#define U_IS_BMP(c) ((uint32_t)(c) <= 0xFFFF)

/**
 * Is this code point a supplementary code point (U+010000..U+10FFFF)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.8
 */
#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x010000) <= 0xFFFFF)

/**
 * Is this code point a surrogate (U+d800..U+dfff)?
 * @param c 32-bit code point
 * @return TRUE or FALSE
 * @stable ICU 2.4
 */
#define U_IS_SURROGATE(c) (((c)&0xFFFFF800) == 0xD800)

/**
 * Get the lead surrogate (0xD800..0xDBFF) for a
 * supplementary code point (0x010000..0x10FFFF).
 * @param supplementary 32-bit code point (U+010000..U+10FFFF)
 * @return lead surrogate (U+D800..U+DBFF) for supplementary
 * @stable ICU 2.4
 */
#define U16_LEAD(supplementary) (UChar)(((supplementary) >> 10) + 0xD7C0)

/**
 * Get the trail surrogate (0xDC00..0xDFFF) for a
 * supplementary code point (0x010000..0x10FFFF).
 * @param supplementary 32-bit code point (U+010000..U+10FFFF)
 * @return trail surrogate (U+DC00..U+DFFF) for supplementary
 * @stable ICU 2.4
 */
#define U16_TRAIL(supplementary) (UChar)(((supplementary)&0x3FF) | 0xDC00)

    // This must be called with the length pre-determined by the first byte.
    // If presented with a length > 4, this returns false.  The Unicode
    // definition of UTF-8 goes up to 4-byte sequences.
    static bool isLegalUTF8(const unsigned char* source, int length)
    {
        unsigned char a;
        const unsigned char* srcptr = source + length;
        switch (length) {
        default:
            return false;
        // Everything else falls through when "true"...
        case 4:
            if ((a = (*--srcptr)) < 0x80 || a > 0xBF)
                return false;
            V8_FALLTHROUGH;
        case 3:
            if ((a = (*--srcptr)) < 0x80 || a > 0xBF)
                return false;
            V8_FALLTHROUGH;
        case 2:
            if ((a = (*--srcptr)) > 0xBF)
                return false;

            // no fall-through in this inner switch
            switch (*source) {
            case 0xE0:
                if (a < 0xA0)
                    return false;
                break;
            case 0xED:
                if (a > 0x9F)
                    return false;
                break;
            case 0xF0:
                if (a < 0x90)
                    return false;
                break;
            case 0xF4:
                if (a > 0x8F)
                    return false;
                break;
            default:
                if (a < 0x80)
                    return false;
            }
            V8_FALLTHROUGH;

        case 1:
            if (*source >= 0x80 && *source < 0xC2)
                return false;
        }
        if (*source > 0xF4)
            return false;
        return true;
    }

    // Magic values subtracted from a buffer value during UTF8 conversion.
    // This table contains as many values as there might be trailing bytes
    // in a UTF-8 sequence.
    static const UChar32 offsetsFromUTF8[6] = { 0x00000000UL,
        0x00003080UL,
        0x000E2080UL,
        0x03C82080UL,
        static_cast<UChar32>(0xFA082080UL),
        static_cast<UChar32>(0x82082080UL) };

    static inline UChar32 readUTF8Sequence(const char*& sequence, size_t length)
    {
        UChar32 character = 0;

        // The cases all fall through.
        switch (length) {
        case 6:
            character += static_cast<unsigned char>(*sequence++);
            character <<= 6;
            V8_FALLTHROUGH;
        case 5:
            character += static_cast<unsigned char>(*sequence++);
            character <<= 6;
            V8_FALLTHROUGH;
        case 4:
            character += static_cast<unsigned char>(*sequence++);
            character <<= 6;
            V8_FALLTHROUGH;
        case 3:
            character += static_cast<unsigned char>(*sequence++);
            character <<= 6;
            V8_FALLTHROUGH;
        case 2:
            character += static_cast<unsigned char>(*sequence++);
            character <<= 6;
            V8_FALLTHROUGH;
        case 1:
            character += static_cast<unsigned char>(*sequence++);
        }

        return character - offsetsFromUTF8[length - 1];
    }

    ConversionResult convertUTF8ToUTF16(const char** sourceStart,
        const char* sourceEnd, UChar** targetStart,
        UChar* targetEnd, bool* sourceAllASCII,
        bool strict)
    {
        ConversionResult result = conversionOK;
        const char* source = *sourceStart;
        UChar* target = *targetStart;
        UChar orAllData = 0;
        while (source < sourceEnd) {
            int utf8SequenceLength = inlineUTF8SequenceLength(*source);
            if (sourceEnd - source < utf8SequenceLength) {
                result = sourceExhausted;
                break;
            }
            // Do this check whether lenient or strict
            if (!isLegalUTF8(reinterpret_cast<const unsigned char*>(source),
                    utf8SequenceLength)) {
                result = sourceIllegal;
                break;
            }

            UChar32 character = readUTF8Sequence(source, utf8SequenceLength);

            if (target >= targetEnd) {
                source -= utf8SequenceLength; // Back up source pointer!
                result = targetExhausted;
                break;
            }

            if (U_IS_BMP(character)) {
                // UTF-16 surrogate values are illegal in UTF-32
                if (U_IS_SURROGATE(character)) {
                    if (strict) {
                        source -= utf8SequenceLength; // return to the illegal value itself
                        result = sourceIllegal;
                        break;
                    }
                    *target++ = replacementCharacter;
                    orAllData |= replacementCharacter;
                } else {
                    *target++ = static_cast<UChar>(character); // normal case
                    orAllData |= character;
                }
            } else if (U_IS_SUPPLEMENTARY(character)) {
                // target is a character in range 0xFFFF - 0x10FFFF
                if (target + 1 >= targetEnd) {
                    source -= utf8SequenceLength; // Back up source pointer!
                    result = targetExhausted;
                    break;
                }
                *target++ = U16_LEAD(character);
                *target++ = U16_TRAIL(character);
                orAllData = 0xFFFF;
            } else {
                if (strict) {
                    source -= utf8SequenceLength; // return to the start
                    result = sourceIllegal;
                    break; // Bail out; shouldn't continue
                } else {
                    *target++ = replacementCharacter;
                    orAllData |= replacementCharacter;
                }
            }
        }
        *sourceStart = source;
        *targetStart = target;

        if (sourceAllASCII)
            *sourceAllASCII = !(orAllData & ~0x7F);

        return result;
    }

    // Helper to write a three-byte UTF-8 code point to the buffer, caller must
    // check room is available.
    static inline void putUTF8Triple(char*& buffer, UChar ch)
    {
        *buffer++ = static_cast<char>(((ch >> 12) & 0x0F) | 0xE0);
        *buffer++ = static_cast<char>(((ch >> 6) & 0x3F) | 0x80);
        *buffer++ = static_cast<char>((ch & 0x3F) | 0x80);
    }

} // namespace

String16::String16(const UChar* characters, size_t size)
    : m_impl(characters, size)
{
}

String16::String16(const UChar* characters)
    : m_impl(characters)
{
}

String16::String16(const char* characters)
    : String16(characters, std::strlen(characters))
{
}

String16::String16(const char* characters, size_t size)
{
    m_impl.resize(size);
    for (size_t i = 0; i < size; ++i)
        m_impl[i] = characters[i];
}

String16::String16(const std::basic_string<UChar>& impl)
    : m_impl(impl)
{
}

// static
String16 String16::fromInteger(int number)
{
    char arr[50];
    v8::internal::Vector<char> buffer(arr, arraysize(arr));
    return String16(IntToCString(number, buffer));
}

// static
String16 String16::fromInteger(size_t number)
{
    const size_t kBufferSize = 50;
    char buffer[kBufferSize];
#if !defined(_WIN32) && !defined(_WIN64)
    v8::base::OS::SNPrintF(buffer, kBufferSize, "%zu", number);
#else
    v8::base::OS::SNPrintF(buffer, kBufferSize, "%Iu", number);
#endif
    return String16(buffer);
}

// static
String16 String16::fromDouble(double number)
{
    char arr[50];
    v8::internal::Vector<char> buffer(arr, arraysize(arr));
    return String16(DoubleToCString(number, buffer));
}

// static
String16 String16::fromDouble(double number, int precision)
{
    std::unique_ptr<char[]> str(
        v8::internal::DoubleToPrecisionCString(number, precision));
    return String16(str.get());
}

int64_t String16::toInteger64(bool* ok) const
{
    return charactersToInteger(characters16(), length(), ok);
}

int String16::toInteger(bool* ok) const
{
    int64_t result = toInteger64(ok);
    if (ok && *ok) {
        *ok = result <= std::numeric_limits<int>::max() && result >= std::numeric_limits<int>::min();
    }
    return static_cast<int>(result);
}

String16 String16::stripWhiteSpace() const
{
    if (!length())
        return String16();

    size_t start = 0;
    size_t end = length() - 1;

    // skip white space from start
    while (start <= end && isSpaceOrNewLine(characters16()[start]))
        ++start;

    // only white space
    if (start > end)
        return String16();

    // skip white space from end
    while (end && isSpaceOrNewLine(characters16()[end]))
        --end;

    if (!start && end == length() - 1)
        return *this;
    return String16(characters16() + start, end + 1 - start);
}

String16Builder::String16Builder() = default;

void String16Builder::append(const String16& s)
{
    m_buffer.insert(m_buffer.end(), s.characters16(),
        s.characters16() + s.length());
}

void String16Builder::append(UChar c) { m_buffer.push_back(c); }

void String16Builder::append(char c)
{
    UChar u = c;
    m_buffer.push_back(u);
}

void String16Builder::append(const UChar* characters, size_t length)
{
    m_buffer.insert(m_buffer.end(), characters, characters + length);
}

void String16Builder::append(const char* characters, size_t length)
{
    m_buffer.insert(m_buffer.end(), characters, characters + length);
}

void String16Builder::appendNumber(int number)
{
    constexpr int kBufferSize = 11;
    char buffer[kBufferSize];
    int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%d", number);
    DCHECK_LE(0, chars);
    m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

void String16Builder::appendNumber(size_t number)
{
    constexpr int kBufferSize = 20;
    char buffer[kBufferSize];
#if !defined(_WIN32) && !defined(_WIN64)
    int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%zu", number);
#else
    int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%Iu", number);
#endif
    DCHECK_LE(0, chars);
    m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

void String16Builder::appendUnsignedAsHex(uint64_t number)
{
    constexpr int kBufferSize = 17;
    char buffer[kBufferSize];
    int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%016" PRIx64, number);
    DCHECK_LE(0, chars);
    m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

void String16Builder::appendUnsignedAsHex(uint32_t number)
{
    constexpr int kBufferSize = 9;
    char buffer[kBufferSize];
    int chars = v8::base::OS::SNPrintF(buffer, kBufferSize, "%08" PRIx32, number);
    DCHECK_LE(0, chars);
    m_buffer.insert(m_buffer.end(), buffer, buffer + chars);
}

String16 String16Builder::toString()
{
    return String16(m_buffer.data(), m_buffer.size());
}

void String16Builder::reserveCapacity(size_t capacity)
{
    m_buffer.reserve(capacity);
}

String16 String16::fromUTF8(const char* stringStart, size_t length)
{
    if (!stringStart || !length)
        return String16();

    std::vector<UChar> buffer(length);
    UChar* bufferStart = buffer.data();

    UChar* bufferCurrent = bufferStart;
    const char* stringCurrent = stringStart;
    if (convertUTF8ToUTF16(&stringCurrent, stringStart + length, &bufferCurrent,
            bufferCurrent + buffer.size(), nullptr,
            true)
        != conversionOK)
        return String16();

    size_t utf16Length = bufferCurrent - bufferStart;
    return String16(bufferStart, utf16Length);
}

std::string String16::utf8() const
{
    size_t length = this->length();

    if (!length)
        return std::string("");

    // Allocate a buffer big enough to hold all the characters
    // (an individual UTF-16 UChar can only expand to 3 UTF-8 bytes).
    // Optimization ideas, if we find this function is hot:
    //  * We could speculatively create a CStringBuffer to contain 'length'
    //    characters, and resize if necessary (i.e. if the buffer contains
    //    non-ascii characters). (Alternatively, scan the buffer first for
    //    ascii characters, so we know this will be sufficient).
    //  * We could allocate a CStringBuffer with an appropriate size to
    //    have a good chance of being able to write the string into the
    //    buffer without reallocing (say, 1.5 x length).
    if (length > std::numeric_limits<unsigned>::max() / 3)
        return std::string();

    std::string output(length * 3, '\0');
    const UChar* characters = m_impl.data();
    const UChar* characters_end = characters + length;
    char* buffer = &*output.begin();
    char* buffer_end = &*output.end();
    while (characters < characters_end) {
        // Use strict conversion to detect unpaired surrogates.
        ConversionResult result = convertUTF16ToUTF8(
            &characters, characters_end, &buffer, buffer_end, /* strict= */ true);
        DCHECK_NE(result, targetExhausted);
        // Conversion fails when there is an unpaired surrogate.  Put
        // replacement character (U+FFFD) instead of the unpaired
        // surrogate.
        if (result != conversionOK) {
            DCHECK_LE(0xD800, *characters);
            DCHECK_LE(*characters, 0xDFFF);
            // There should be room left, since one UChar hasn't been
            // converted.
            DCHECK_LE(buffer + 3, buffer_end);
            putUTF8Triple(buffer, replacementCharacter);
            ++characters;
        }
    }

    output.resize(buffer - output.data());
    return output;
}

} // namespace v8_inspector
